The Astron BB-30M battery backup module automatically switches to the battery source upon power supply failure (battery not provided). It also serves as a built-in battery charger for standard 12 and 24 volt batteries (13.8 and 27.6VDC). The battery and power supply sources may combine during peak power events. Built-in fuse (two 15 amp auto type) protection on battery charging and discharging. There is a front panel 3-way LED that indicates battery charged, is charging or on battery back-up. Maximum load is 30 amps. Charging current is 3.6 amps. 3.8 x 4.5 x 1.93 inches 1.5 lbs. Click here for other view. One year manufacturer's limited warranty. Backup battery is not included.